Padlock

ABSTRACT

A padlock of hardened steel having a lock mechanism inserted through an opening in the lock casing, which opening is covered by a cover plate with a very shallow surface hardening. The cover plate is initially curved and is pressed flat to fill a conical attachment recess in the lock casing.

United States Patent Burakoff et al. 1 Jan. 25, 1972 4] PADLOCK [56]References Cited [72] Inventors: Valdemar Burakoif; Paul Kraltstrom;Into UNITED STATES PATENTS Sinervo' Kaarlo Solitanner, all of H l k',Finland e Sm 2,070,012 2 1937 Jacobi ..70/52 x [73] Assignee: 0yWartsila Ab, Helsinki, Finland FOREIGN PATEN 0R APPLICATIONS 22 Filed;Au 28, 19s; 28,275 9/1956 Finland ..70/38 [21] Appl' 755969 PrimaryExaminer-Marvin A. Champion Assistant Examiner-Edward J. McCarthyAllorneywaters Roditi, Schwartz & Nissen [30] Foreign ApplicationPriority Data Aug. 29, 1967 Finland ..23l5/67 [57] ABSTRMT A padlock ofhardened steel having a lock mechanism inserted CL 2 through an openingin the lock casing, which opening is [51] Int. Cl. ..E05b 67/22, E05b67/02 covered by a cover plate with a very shallow surface harden- [58]Field of Search ..70/5 1 52, 38, 38 A, 38 B, ing. The cover plate isinitially curved and is pressed flat to fill a conical attachment recessin the lock casing.

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13 Claims, 1 Drawing Figure PADLOCK The present invention relates to apadlock comprising a lock casing, a lock shackle to be locked in thelock casing, and a lock bolt providing a locking action and beingmovable inside the lock casing and operable by a lock mechanism.

Various attempts have been made to produce unbreakable padlocks byattaching protecting plates or bars of hardened steel or other hardmaterial to the lock casing, but in spite of these efforts, no one hasso far succeeded in making an unbreakable lock. Not even the making of acompletely hardened lock casing has met with success for the reason thatthe lock mechanism has to be inserted into the lock casing andthereafter the lock casing has to be closed in such a way that it cannotbe reopened. The closing of the lock casing is usually made by pressinga cover plate into an attachment recess so that it undergoes a plasticdeformation and fills the attachment recess, after which the outersurface of the lock casing is ground even, so that the cover platecannot be grabbed by any tool. As this way of closing the lock casingpresupposes plastic deformation of the cover plate, a hardened coverplate cannot be used, and hence, there will be a weak spot just in frontof the lock mechanism even if the other parts of the lock casing arehardened.

The object of the invention is to provide a very strong, practicallyunbreakable lock, which cannot be broken by means of sawing, boring orheavy overloading, for instance by means of an iron bar. The inventionis characterized in that the outside surface of the lock casing iscompletely hardened and that in the lock casing, preferably in one ofits ends, there is an opening for the insertion of the lock mechanisminto the lock casing, which opening is covered by a cover plate whichhas a shallow surface hardening so that its attachment into anattachment groove or slot by means of bending is possible. The inventionis based on'the observation that a plate having a shallow surfacehardening can be bent somewhat without damaging the hardened surface,and that such a slight bending is sufficient for the attachment of theplate in a lock casing. It has also been found that even a shallowsurface hardening effectively prevents boring and sawing with ordinarytools. Accordingly the invention makes it possible to create a lockcasing with a completely hardened outer surface.

Usually the best results are obtained if the hardness penetration in thecover plate is a maximum of 0.1 mm., preferably 0.07 mm. at a maximum.The hardness penetration on the inner surface of the cover plate may bethe same. The inner surface may also be left unhardened, but this causeshigher production costs.

The cover plate is most suitably attached in a conical recess into whichthe initially convex cover plate can be inserted, and thereafter bypressing the cover plate flat it can be made to completely fill saidrecess. The opening covered by the cover plate is preferably made in theshackle end of the lock casing, because this part is protected by theshackle and by the attachment irons of the lock.

The complete surface hardening of the lock casing prevents breaking thelock by means of boring or sawing. In order that the lock alsowithstands breaking attempts by means of overloading, the strength ofthe lock can be improved by rounding the shackle facing edges of theguide borings for the lock bolts at least above the lock bolt. It hasbeen found that the strength of the lock may be increased by more thanpercent if the radius of the rounding is 0.4 to 1.2 mm.

The strength and general durability of the lock can be further improvedby making the lock casing of substantially rectangular bar stock whichis provided with two borings for the shackle and one boring for the lockmechanism which preferably is a cylinder lock. In this way also theproduction costs of the lock are substantially reduced.

A lock according to the invention should of course be designed towithstand all kinds of known destroying methods, otherwise its strengthin some respects is useless; One known method to break a padlock byforce is to load the lock mechanism axially through the key hold with avery great force in order to press out the cover plate in the oppositeend of the lock from the inside. The durability of the lock againstbreaking attempts of this kind can be very much improved by locking thelock mechanism axially by means of a locking ring or the like. This ringshould be situated in such a way that it resists at least a part of theaxial load which may be applied to the lock mechanism through thekeyhole. In this way the strength of the lock can be made up to fourtimes greater.

In the following, one embodiment of the invention will be described morefully with reference to the attached drawing showing an axial section ofa padlock according to the invention.

In the drawing, 1 indicates the lock casing having a completely hardenedouter surface, 2 the shackle, 3 the lock bolts and 4 a cylinder lockmechanism. In the lock casing I there are two borings 5 for the shackle2 and a third boring 6 for the cylinder lock 4. The boring 6 is closedby a cover plate 7 which is attached in a conical recess 8. In theillustrated embodiment, the cone angle is about 40 which has been foundsuitable. The cone angle should be 20 to 60", preferably 30 to 50 inorder to obtain a reliable attachment of the cover plate 7. The coverplate 7 is initially somewhat convex, so that its edge surface is moreor less cylindrical. When the convex plate is pressed flat, its edgesurface becomes conical and is pressed against the corresponding conicalside surface of the recess 8. The deformation of the cover plate 7 is sosmall, that the cover plate can be surface hardened if the hardnesspenetration is a maximum 0.1 mm. In practice a hardness penetration of0.05 to 0.06 mm. gives the best results.

The lock bolts 3 are movable in borings 9. The movement is obtained byturning the cylinder of the lock mechanism 4, whereby a plate 10 at theend of the cylinder pushes the lock bolts 3 outwards. In the oppositedirection, the bolts 3 move by being pushed by the inclined surfaces ofthe shackle 2. The edges of the borings 9 facing the shackle 2 are atleast on the upper side, rounded with a radius r, of about 0.4 to 1.2mm. It has been found, that a radius of 0.5 mm. can increase thestrength of the lock by more than 10 percent. This is due to the fact,that part of the shearing stress of the lock bolts is transformed intobending stress. If the rounding radius r is made too large, the strengthof the lock decreases. The plate 10 should be of such a hard materialthat it is not deformed by the load of the lock bolts when the shackleis pulled outwards with a great force.

In the boring 6 there is a locking ring 11 above the lock cylinder ofthe lock mechanism. If the lock cylinder is loaded axially through thekey hole, the lock cylinder will reach the locking ring 11 at the sametime that the plate 10 reaches the cover 7. The cover 7 and the lockingring 11 will then both take up the axial load and in this case the lockmay withstand a load of the order discussed of more than 5,000 kp.

The invention is not limited to the embodiment shown, but severaldifierent modifications of the invention are feasible within the scopeof the following claims.

What is claimed is:

l. A padlock comprising a lock casing, a shackle to be locked in saidlock casing and at least one lock bolt providing a locking action andbeing movable in said lock casing and operable by a lock mechanism; animprovement wherein the outside surface of said lock casing iscompletely hardened and said lock casing is provided with an opening forthe insertion of the lock mechanism into said lock casing, a cover platefor closing said opening, said cover plate having a shallow surfacehardening to allow said cover plate to be attached into an attachmentgroove at said opening by means of a slight bending.

2. A lock according to claim 1 wherein a conical recess for said coverplate is provided in said lock casing, said cover plate being initiallycurved and inserted into said recess by being pressed flat.

3. A lock according to claim 2 wherein said recess has a cone angle of20 to 60'.

4. A lock according to claim 2 wherein said recess has a cone angle of30 to 50.

5. A lock according to claim I wherein said casing has a guiding borefor movement of said lock bolt, said guiding bore having a rounded edgeadjacent said shackle.

6. A lock according to claim 5 wherein said rounded edge has a radius of0.4 to 1.2 mm.

7. A lock according to claim 2 wherein said cover plate is initiallyconvex with a cylindrical edge, the latter edge. being locked in saidconical recess when the cover plate is pressed flat and pennaneritlydeformed in said recess.

8. A lock according to claim 1, wherein the hardness penetration in saidcover plate is a maximum of 0.1 mm.

9. A lock according to claim 8, wherein said hardness penetration is amaximum of 0.07 mm.

10. A lock according to claim 1, wherein said opening is situated in thepart of said lock casing facing said shackle.

11. A lock according to claim 1, comprising a locking ring arranged toresist at least part of an axial load applied to aid lock mechanismthrough the keyhole of said padlock.

12. A lock according to claim 1, wherein said lock casing is made ofsubstantially rectangular bar stock and is provided with two borings forsaid shackle and one boring for said lock mechanism.

13. A lock according to claim 1, wherein said lock mechanism is acylinder lock mechanism.

a: r e

1. A padlock comprising a lock casing, a shackle to be locked in said lock casing and at least one lock bolt providing a locking action and being movable in said lock casing and operable by a lock mechanism; an improvement wherein the outside surface of said lock casing is completely hardened and said lock casing is provided with an opening for the insertion of the lock mechanism into said lock casing, a cover plate for closing said opening, said cover plate having a shallow surface hardening to allow said cover plate to be attached into an attachment groove at said opening by means of a slight bending.
 2. A lock according to claim 1 wherein a conical recess for said cover plate is provided in said lock casing, said cover plate being initially curved and inserted into said recess by being pressed flat.
 3. A lock according to claim 2 wherein said recess has a cone angle of 20* to 60*.
 4. A lock according to claim 2 wherein said recess has a cone angle of 30* to 50*.
 5. A lock according to claim 1 wherein said casing has a guiding bore for movement of said lock bolt, said guiding bore having a rounded edge adjacent said shackle.
 6. A lock according to claim 5 wherein said rounded edge has a radius of 0.4 to 1.2 mm.
 7. A lock according to claim 2 wherein said cover plate is initially convex with a cylindrical edge, the latter edge being locked in said conical recess when the cover plate is pressed flat and permanently deformed in said recess.
 8. A lock according to claim 1, wherein the hardness penetration in said cover plate is a maximum of 0.1 mm.
 9. A lock according to claim 8, wherein said hardness penetration is a maximum of 0.07 mm.
 10. A lock according to claim 1, wherein said opening is situated in the part of said lock casing facing said shackle.
 11. A lock according to claim 1, comprising a locking ring arranged to resist at least part of an axial load applied to said lock mechanism through the keyhole of said padlock.
 12. A lock according to claim 1, wherein said lock casing is made of substantially rectangular bar stock and is provided with two borings for said shackle and one boring for said lock mechanism.
 13. A lock according to claim 1, wherein said lock mechanism is a cylinder lock mechanism. 